Two oxygenated fuels used as a substitute for petroleum diesel fuel, namely biodiesel and dimethyl ether (DME), were experimentally investigated in a single-cylinder diesel engine equipped with a common-rail fuel injection system. The effects of oxyge ...
Two oxygenated fuels used as a substitute for petroleum diesel fuel, namely biodiesel and dimethyl ether (DME), were experimentally investigated in a single-cylinder diesel engine equipped with a common-rail fuel injection system. The effects of oxygenated fuels on the injection rate, combustion, exhaust emission, and particle size distribution were examined in order to find a way to achieve the effective reduction of exhaust emissions. In addition, two low emission strategies, multiple injection and premixed charge compression ignition (PCCI) combustion, were investigated as part of efforts to explore possible solutions when it comes to meeting future emission regulations.
In addition, the injection rate, combustion, and emissions were examined under various operating conditions in order to study the effect of biodiesel fuel. The scanning mobility particle sizer (SMPS) system was used for the size distribution analysis. To this end, a mobility equivalent particulate diameter in the range of 10.4 to 392.4 nm was identified. The effect of various operating conditions and multiple injection parameters on the particle size distribution of biodiesel and conventional diesel fuel was also investigated.
Combustion and the emission characteristics of DME as a fuel for compression ignition (CI) engines were evaluated by comparing the results of DME with those obtained from conventional diesel fuel. In terms of DME fuel, most efforts were devoted to reducing NOx emission as DME fueled engines were found to emit virtually no soot. Multiple injection strategies that included pilot injection, split injection, and partial premixed charge compression ignition (PPCCI) combustion were applied to this end, and the optimum injection parameters for multiple injection strategies were derived. In addition, a new combustion concept known as a narrow angle direct injection (NADI) strategy was attempted in order to achieve a dramatic reduction in NOx. In order to achieve this concept, a narrow spray angle injector, modified piston geometry, and reduced compression ratio were implemented.
The study revealed that while the use of biodiesel simultaneously reduced soot, hydrocarbon (HC), and carbon monoxide (CO) emissions, a slight increase in nitrogen oxide (NOx) emissions occurred. Compared to diesel fuel, the combustion of biodiesel fuel reduced a relatively larger diameter range of particulate concentration where most of the particulate mass is found. Multiple injections of biodiesel fuel also resulted in a simultaneous reduction in NOx. Moreover, the pilot injection of biodiesel at optimum timing was also found to reduce larger size particles.
Undetectable soot emission was indicated throughout the operating conditions when the engine was fueled with DME. However, DME also increased NOx emissions at the same injection timing as diesel fuel. The multiple injection strategies of split injection and pilot injection made significant decreases in NOx emission with a slight expense of the indicated mean effective pressure (IMEP) possible. PPCCI combustion created by dividing injection event into two injections, namely early and late injection, allowed the most significant reduction in NOx emission. However, the inordinate advance of the combustion phase ushered in by early injection had the effect of deteriorating the IMEP. The implementation of the NADI configuration and early injection resulted in extremely low NOx emissions and a moderate IMEP in the case of both diesel and DME fuel.